JP2002159598A - Mold for golf ball, and golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for a golf ball capable of giving a golf ball having an excellent aerodynamic characteristic and facilitating the manufacture of golf balls. SOLUTION: This mold for golf ball is formed of an upper mold 1 and a lower mold 3. A cavity surface 5 of the upper mold 1 and the lower mold 3 are provided with multiple projections 7 to form dimples. A mating surface between the upper mold 1 and the lower mold 3 is formed into an irregular surface. In each upper mold 1 and lower mold 3, the number of projecting part and recessed part is set at 3-5. In each projecting part, 2-8 projections 7 exist in the first line from the mating surface. In each projecting part, at least one of the projections 7 of the first line from the mating surface satisfies a following mathematical expression I. In this mathematical expression I, R means a radius of the corresponding projection 7, and L means a straight distance in the vertical direction between the center of the corresponding projection 7 and the mating surface. R×0.8<=L<=R×1.2...(I).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf ball mold.

[0002]

2. Description of the Related Art A golf ball has about 300 to 550 dimples on its surface. The role of the dimple is to disturb the flow of air around the golf ball during the flight of the golf ball, thereby promoting turbulent transition of the boundary layer and causing turbulent separation (hereinafter referred to as the “dimple effect”). .). By promoting the turbulent transition, the separation point of the air from the golf ball is lowered backward, the pressure resistance is reduced, and the flight distance of the golf ball is increased. Further, by promoting the turbulent transition, the difference in the separation point between the upper side and the lower side of the golf ball due to the back spin is promoted, and the lift acting on the golf ball is increased.

A golf ball is usually formed by a mold having an upper mold and a lower mold each having a hemispherical cavity. When the upper mold cavity is assumed to be the northern hemisphere of the globe and the lower mold cavity is assumed to be the southern hemisphere of the globe, the upper mold and the lower mold are matched on the equatorial plane (a plane including the equator). There are many protrusions on the inner peripheral surface of the mold,
These projections form dimples on the surface of the golf ball. Therefore, the shape of the dimple is a shape obtained by inverting the shape of the protrusion.

Since molding material (for example, synthetic resin) leaks from the joint between the upper mold and the lower mold, burrs are generated at a portion corresponding to the equator on the surface of the golf ball. This burr is ground and removed with a grindstone or the like. If burrs are formed inside the dimples, it is difficult to remove the burrs. In many cases, no dimples are formed on the equator for easy removal of burrs. That is, in many cases, no projection is provided at the joint of the molds. Thus, a great circle path that is a great circle that does not intersect with the dimple is formed on the surface of the golf ball. If the portion of the great circle path where the peripheral speed of the back spin is the fastest (hereinafter also referred to as the “fastest portion”) matches, a sufficient dimple effect cannot be obtained and the flight distance becomes insufficient. In addition, the dimple effect obtained when the great circle path coincides with the fastest part is different, so that the aerodynamic symmetry of the golf ball is inferior. The dimple in the vicinity of the great circle passage may be slightly deformed when the burr is removed, and when this deformation occurs, the dimple effect when the large circle passage and the fastest part coincide with each other becomes further insufficient.

[0005] JP-A-62-47379, JP-A-Hei-8
JP-173576A and JP-A-11-137727 disclose a golf ball molding die in which an upper die and a lower die have a convex part and a concave part, and a mating surface between the upper die and the lower die has an irregular shape. ing. In this mold, burrs are generated in an uneven shape. Therefore, even when a dimple-forming projection is provided on the equator, burrs can be generated by avoiding the dimple. Therefore, burrs are relatively easily removed. However, if the projection is located on the mating surface in this mold, burrs will also be generated inside the dimple. In order to remove burrs, projections must be arranged avoiding the mating surface. As a result, in the obtained golf ball, many band-shaped smooth portions (portions where no dimples exist) along the mating surface are generated. This band-shaped smooth portion has a relatively large area, and does not coincide with the equator, but is concentrated near the equator, and extends almost parallel to the equator. Therefore, the dimple effect when the equator coincides with the fastest part of the backspin is still insufficient.

In Japanese Patent Application Laid-Open No. Sho 61-173907, a dimple-forming projection is provided on the equator.
A golf ball mold in which convex portions and concave portions are alternately arranged at individual pitches is disclosed. Since the mating surface of the golf ball mold is a so-called wave shape, the golf ball hardly has a band-like smooth portion. However, in this mold, it is necessary to provide an extremely large number of convex portions and concave portions, so that it is difficult to manufacture the mold.

Japanese Patent Application Laid-Open No. Hei 10-127826 discloses a golf ball mold in which a flat surface coinciding with the equatorial plane is provided between a convex portion and a concave portion. This mold is for injection molding and has a flat surface provided with a gate for injecting molding material. In this mold, since a flat surface is provided between adjacent projections on the equatorial plane, the interval between the projections cannot be reduced, and the degree of freedom in designing a dimple pattern is poor. Further, since the mating surface between the upper mold and the lower mold has a double step, it is extremely troublesome to manufacture the mold.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a golf ball molding die which can obtain a golf ball having excellent aerodynamic characteristics and can be easily manufactured. It is the purpose.

[0009]

The invention made to achieve the above object comprises an upper die and a lower die having a large number of dimple-forming projections on a cavity surface thereof. Each has a convex part and a concave part which are alternately arranged so that a mating surface with a counterpart becomes uneven, and the convex part of the upper die, the concave part of the upper die, the convex part of the lower die and the concave part of the lower die are provided. Are 3 or more and 5 or less in each case. Each projection has two or more and eight or less projections in the first row from the mating surface. At least one of the projections in the first row is a golf ball mold configured to satisfy the following formula (I). R × 0.8 ≦ L ≦ R × 1.2 (I) (In the formula (I), R represents the radius of the projection, and L represents the vertical linear distance between the center of the projection and the mating surface.) Represents.)

[0010] A golf ball obtained from this mold does not have a wide area band-shaped smooth portion. Moreover, even when the edge of the dimple is deformed due to the removal of the burr, the deformed portion does not line up along the great circle. Therefore,
This golf ball has excellent aerodynamic characteristics. In addition, this mold is relatively easy to manufacture, and has less restrictions on the design of the dimple pattern.

[0011] Preferably, the protrusions are arranged such that there is no great circle path which is a great circle which does not intersect with the dimple on the surface of the golf ball to be molded. A golf ball obtained from this mold has more excellent aerodynamic characteristics.

Preferably, a gate for injecting molding material is provided at a position where the mating surface and the equatorial plane intersect. Although this mold is for injection molding, it has excellent dimple pattern design flexibility and is easy to manufacture.

Preferably, in each of the upper mold and the lower mold, the mating surface with the counterpart is a convex surface which is in the convex portion and is substantially parallel to the equatorial plane, a concave surface in the concave portion which is substantially parallel to the equatorial surface, and a convex and concave surface. And a boundary surface located between Then, all the convex surfaces have the same area, all the concave surfaces have the same area, and both the convex surface and the concave surface have the same area. In this molding die, the pressing force at the time of molding the golf ball is uniformly dispersed in the molding die, so that the obtained golf ball is homogeneous.

Preferably, in each of the upper die and the lower die, the difference in height between the highest convex portion and the lowest concave portion is 2.
0 mm or less. This mold is easily manufactured, and the golf ball after molding is easily taken out of the mold.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
The present invention will be described in detail based on embodiments.

FIG. 1 shows a golf ball mold according to an embodiment of the present invention (hereinafter, also simply referred to as “mold”).
FIG. This mold comprises an upper mold 1 and a lower mold 3. When the upper mold 1 and the lower mold 3 are combined, a spherical cavity is formed. The cavity forms a golf ball. A number of projections 7 are provided on the cavity surface 5 of the upper mold 1 and the lower mold 3. The contour of the projection 7 is a circle. The projections 7 form dimples on the surface of the golf ball. As is clear from FIG. 1, the mating surface of the upper mold 1 and the lower mold 3 (the surface where the upper mold 1 and the lower mold 3 come into contact when the mold is clamped) is uneven. The two-dot chain line indicated by the symbol E in FIG.
The uppermost part of the cavity surface 5 of the upper die 1 is the north pole Pn of the globe
Is the equator when the bottom of the lower mold 3 is assumed to be the south pole Ps of the globe. The plane including the equator E is an equatorial plane.

FIG. 2 is a perspective view showing the lower mold 3 of the mold shown in FIG. The lower die 3 has five convex portions 9 and five concave portions 11. The protrusion 9 is a portion protruding from the equator E. The concave portion 11 is a portion depressed from the equator E. The convex portions 9 and the concave portions 11 are arranged alternately.
Although not shown, the upper mold 1 also has five protrusions 9 and 5 similarly.
And a plurality of recesses 11. The convex part 9 of the lower mold 3 is the upper mold 1
Of the lower die 3 and the upper die 1
Is fitted. By this fitting, a spherical cavity is formed as described above, and the mating surface of the upper mold 1 and the lower mold 3 becomes uneven.

Since the convex portions 9 and the concave portions 11 are alternately arranged as described above, the number of the convex portions 9 and the number of the concave portions 11 in the lower mold 3 are the same (five in this example). . Lower mold 3
Are fitted into the concave portions 11 of the upper die 1, so that the number of the concave portions 11 of the upper die 1 is the same as the number of the convex portions 9 of the lower die 3.
Since the protrusions 9 of the upper mold 1 are fitted into the recesses 11 of the lower mold 3, the number of the protrusions 9 of the upper mold 1 is the same as the number of the recesses 11 of the lower mold 3. That is, in this molding die, the convex portion 9 of the upper die 1,
The concave portion 11 of the upper die 1, the convex portion 9 of the lower die 3, and the concave portion 1 of the lower die 3.
The number of 1s is the same.

In the lower die 3, the mating surface with the upper die 1 comprises a convex surface 13, a concave surface 15, and a boundary surface 17. The convex surface 13 is a surface in the convex portion 9 and substantially parallel to the equatorial plane.
The concave surface 15 is a surface in the concave portion 11 and substantially parallel to the equatorial plane. The boundary surface 17 is a surface located between the convex surface 13 and the concave surface 15. In the lower mold 3, the upper half of the boundary surface 17 exists in the convex portion 9, and the lower half exists in the concave portion 11. The boundary surface 17 is a plane inclined obliquely to the equatorial plane,
It may be a plane extending in the vertical direction. In the lower die 3, the convex surface 13, the concave surface 15, and the boundary surface 17 are flat surfaces, but may be curved surfaces. Similarly, the mating surface of the upper mold 1 also includes a convex surface 13, a concave surface 15, and a boundary surface 17.

In the lower mold 3, it is preferable that the area of the convex surface 13 and the area of the concave surface 15 are the same. Since the concave surface 15 of the upper die 1 contacts the convex surface 13 of the lower die 3, they have the same area. The convex surface 13 of the upper die 1 is the concave surface 1 of the lower die 3.
Since they are in contact with No. 5, both have the same area. Since the area of the convex surface 13 and the area of the concave surface 15 in the lower mold 3 are the same, the area of all the convex surfaces 13 included in the mold becomes the same, and the area of all the concave surfaces 15 becomes the same. That is, the area of all the convex surfaces 13 and the area of all the concave surfaces 15 included in the mold become the same. During molding of the golf ball, the molding die is pressed by a press or the like, but since all the convex surfaces 13 and the concave surfaces 15 have the same area, the pressing force is uniformly dispersed. As a result, variations in dimensions and physical property values for each region in one golf ball are suppressed. From the viewpoint of uniform dispersion of the pressing force during molding, it is preferable that all the convex surfaces 13 have the same height, that is, all the concave surfaces 15 have the same depth.

FIG. 3 is an enlarged view showing a part of the lower mold 3 of FIG. In this figure, the cavity surface 5 of the lower mold 3 is shown. Hereinafter, the lower mold 3 will be described in detail. The configuration of the upper mold 1 is the same as that of the lower mold 3. Three of the numerous protrusions 7 shown in FIG. 3, indicated by reference numerals 7a, 7b, and 7c, are present on the protrusion 9 (that is, the portion above the equator E), and have a mating surface (convex surface 13). Projection 7 in the first row from
It is. The projections 7 that are present on the projections 9 and are in the first row from the mating surface are all or partially included in the projections 9, and extend vertically from the center to the mating surface of the projections 9. This means that the line segment does not intersect with the other protrusions 7.

When molding a golf ball, burrs are formed on the mating surface. To remove burrs, protrusions 7
Is not formed. As a result, a band-shaped smooth region is generated near the mating surface. In FIG. 3, the band-shaped smooth area is filled with halftone dots. The band-shaped smooth region is concentrated near the equator E, and extends substantially parallel to the equator. Therefore, if the area of the band-shaped smooth portion is large, the resulting golf ball also has a wide area of the band-shaped smooth portion, and the dimple effect when the equator coincides with the fastest part of the back spin becomes insufficient. If the number of the convex portions 9 (also the number of the concave portions 11) in the lower mold 3 is three or more, the area of each band-shaped smooth portion does not increase so much, and therefore, when the equator coincides with the fastest part of the back spin. Of the dimple effect is suppressed. From the viewpoint of suppressing the reduction of the dimple effect, it is preferable that the number of the protrusions 9 is large. However, if the number is too large, it becomes difficult to manufacture a molding die. Therefore, the number of the protrusions 9 is set to five or less.

The number of projections 7 in the first row existing in one projection 9 is two or more and eight or less. If the number is less than two, the area of the belt-shaped smooth portion becomes large, and the dimple effect when the equator coincides with the fastest part of the backspin may be insufficient. From this viewpoint, the number of the protrusions 7 is three.
Or more is preferred. Conversely, when this number exceeds 8, individual dimples become small, and the flight distance of the golf ball may decrease. In this respect, the number of the protrusions 7 is preferably equal to or less than six.

In FIG. 3, what is indicated by a double-headed arrow R is the radius of the first row of projections (projections 7c in the example of this figure) existing in the projections 9. Also, what is indicated by the double-headed arrow L is the vertical linear distance between the center of the projection 7c and the mating surface (convex surface 13). This distance L is measured on the projection plane as shown in FIG. When the boundary surface 17 exists in the vertical direction of the center of the projection 7c, the distance from the center of the projection 7 to the intersection of the boundary surface 17 and a straight line extending in the vertical direction from the center of the projection 7 is L. Is done. At least one of the projections 7 in the first row existing in each of the projections 9 must satisfy the above formula (I). That is, the projections 7 are arranged such that the distance L is at least 0.8 times and at most 1.2 times the radius R. When the distance L is 0.8 times or more and less than 1.0 times the radius R, the projection 7 intersects with the convex surface 13. In this case, the portion of the projection 7 that protrudes from the projection 9 is missing. Accordingly, a part of the dimple formed by the projection 7 is also missing. When the distance L is 1.0 times the radius R, the protrusion 7 contacts the convex surface 13. When the distance L is more than 1.0 times the radius R and not more than 1.2 times, there is some smooth portion between the projection 7 and the convex surface 13. By setting the distance L to be 0.8 times or more and 1.2 times or less the radius R, it is possible to suppress a reduction in appearance due to a large loss of dimples, and to suppress a reduction in aerodynamic characteristics due to a wide-area smooth portion. In this respect, the distance L is preferably 0.8 times or more and 1.0 times or less the radius R. In addition, from the viewpoint of suppressing a reduction in appearance, the width of the missing portion of the protrusion 7 (vertical linear distance) is preferably 1/5 or less of the radius R.

As is apparent from FIG. 3, the projections 7a, 7
b and 7c cross the equator E. Therefore, the golf ball obtained from this mold does not have a great circle path along the equator E. By devising the arrangement of the protrusions 7 in a region other than the vicinity of the equator E, a golf ball having no great circle path at all can be obtained. Golf balls having no great circle path at all have excellent aerodynamic characteristics. Of course, the equator E and other parts may be made into great circle paths. Even in this case, by using the molding die of the present invention, it is possible to avoid a portion where the dimple is deformed due to the removal of burrs from coincident with the great circle passage.

A hemisphere is divided into a plurality of units (this is an arc along the longitude line of the globe, having a length of 1/4 of a great circle, and one end located at a pole). There is also a golf ball that adopts a method in which a unit is divided into spherical isosceles triangles and the dimple pattern of all units is the same. This technique is referred to as the “hemispherical repetitive array method”. In the hemispherical repetitive arrangement method, the aerodynamic symmetry of the golf ball tends to be impaired. By using the molding die shown in FIG. 1 and a golf ball having no great circle path at the equator E,
Aerodynamic symmetry is enhanced even when dimples are arranged by the hemispherical repetitive arrangement method. In the formation of a golf ball in which dimples are arranged by the hemisphere repetition arrangement method, the number of projections 9 in each of the upper mold 1 and the lower mold 3 is the same as the number of units in the hemisphere, or 2 of the number of units in the hemisphere. Preferably it is doubled. Thereby, the aerodynamic symmetry of the golf ball is further enhanced, and the manufacturing cost of the mold is suppressed.

In each of the upper mold 1 and the lower mold 3, the height difference (maximum step) between the highest convex portion 9 and the lowest concave portion 11 is preferably 2.0 mm or less. Maximum step is 2.0
Molds of less than mm do not involve much difficulty in production. In addition, removal (removal) of the molded golf ball is easy. In this respect, the maximum step is particularly preferably equal to or less than 1.5 mm. If the maximum step is too small, the belt-like smooth portion approaches the equator E, and the aerodynamic characteristics of the golf ball deteriorate. Therefore, the maximum step is 0.2 mm or more, and moreover, it is 0.1 mm.
5 mm or more, particularly preferably 1.0 mm or more. In addition,
When the convex surface 13 is a curved surface, the height of the highest portion of the convex surface 13 is set as the height of the convex portion 9. Also, concave surface 1
When 5 is a curved surface, the height of the lowest portion of the concave surface 15 is set as the height of the concave portion 11.

As shown in FIG. 3, a gate 19 is provided on the boundary surface 17. Gate 19 is located at interface 17
Is formed by shaving. This gate 1
9 is a passage when the molding material is injected into the cavity. Usually, the cross-sectional shape of the gate 19 is circular. The gate 19 shown in FIG. 3 has a semicircular cross section, but the remaining semicircular portion is provided on the boundary surface 17 of the upper die 1. By combining the upper mold 1 and the lower mold 3, one gate 19 having a circular cross section is formed. The gate 19 is located on the equator E so that the supply of the molding material to the cavity of the upper mold 1 and the supply of the molding material to the cavity of the lower mold 3 are equal. That is, the gate 19 is provided at a position where the boundary surface 17 (matching surface) and the equatorial plane intersect.

A gate may be provided so as to penetrate the lower end of the projection 9, but in this case, the projection 7
There is a restriction on the degree of freedom of the arrangement. Also, Japanese Patent Application Laid-Open No. 10-1
As disclosed in Japanese Patent No. 27826, the boundary surface 17 may be composed of two inclined surfaces and one horizontal surface, and a gate may be formed on this horizontal surface. However, in this case, processing of the mating surface is troublesome. Therefore, as shown in FIG. 3, it is most preferable that all the gates 19 are provided on the boundary surface 17 which is a single surface. In addition, the injection molding die requires the gate 19 for injection of the molding material, but the compression molding die does not require the gate 19.

FIG. 4 is a plan view showing a golf ball according to one embodiment of the present invention. FIG. 5 is a front view thereof. This golf ball has a diameter of 4.1 mm.
Has 70 dimples A, 210 dimples B having a diameter of 3.80 mm, and 130 dimples C having a diameter of 3.35 mm. The total number of dimples is 410
Individual. The dimple pattern of this golf ball is
They are arranged by the hemispherical repetition arrangement method. The number of units per hemisphere is five. In FIG. 4, the area between the line segment L1 and the line segment L2 is one unit. The dimple pattern in each unit is mirror symmetric. FIG.
Shows the types of dimples in a further half area of one unit.

This golf ball is molded from a molding die in which the mating surface of the upper die and the lower die is uneven. The two-dot chain line shown in FIG. 5 is a line corresponding to the mating surface of the mold. The mating surface of this mold comprises a convex surface, a concave surface and a boundary surface. All convex surfaces and all concave surfaces have the same area. All convex surfaces are 0.4 mm high from the equatorial plane. Therefore, the maximum step of this mold is 0.8 mm. The number of protrusions in each of the upper mold and the lower mold is the same as the number of units per hemisphere (that is, 5).

This golf ball is formed by an injection molding method. The molding die is provided with ten molding material injection gates. All gates are provided at positions where the boundary surface and the equatorial plane intersect.

X, Y and Z correspond to the portions corresponding to the respective convex portions.
There are three dimples. The dimple X and the dimple Z are dimples at geometrically equivalent positions, and are B dimples having a diameter of 3.80 mm. The dimple X and the dimple Z are dimples formed by protrusions that are in contact with the convex surface. Dimple Y
Is a C dimple having a diameter of 3.35 mm. The dimple Y is formed by a projection that intersects with the convex surface. The distance between the center of the protrusion forming the dimple Y and the convex surface is 1.52 mm, which is 0.91 times the radius of the C dimple. There is no great circle path in this golf ball.

The diameter of the dimple formed on the golf ball is not particularly limited, and is usually 2.0 mm or more and 5 mm or less, particularly 2.5 mm or more and 4.5 mm or less. Further, non-circular dimples may be provided instead of or together with the circular dimples. In the case of a non-circular dimple, the diameter of the circle having the smallest diameter among the circles including the non-circular dimple is referred to as the dimple diameter for convenience.

[0035]

EXAMPLES Hereinafter, the effects of the present invention will be clarified based on examples, but it should be understood that the present invention should not be construed as being limited based on the description of the examples.

[Embodiment] A molding die comprising an upper die and a lower die each having five projections was prepared. A core made of solid rubber was charged into this mold, and an ionomer resin composition was injection molded around the core from ten gates to form a cover layer. The surface of this cover layer was coated to obtain a golf ball having a dimple pattern whose plan view is FIG. 4 and whose front view is FIG. The diameter of this golf ball was about 42.7 mm, and the compression (the amount of deformation from the stage at which an initial load of 98 N was applied to the stage at which a final load of 1275 N was applied) was about 3.00 mm. The total dimple volume of this golf ball (total volume of a portion surrounded by the plane including the contour of the dimple and the dimple surface) was about 320 mm ³ .

Comparative Example A golf ball of a comparative example having a dimple pattern having a plan view of FIG. 6 and a front view of FIG. 7 was obtained in the same manner as in the example except that the mold was changed.
This mold includes an upper mold and a lower mold each having a hemispherical cavity, and a mating surface between the upper mold and the lower mold is a flat surface. The two-dot chain line shown in FIG. 7 is a line corresponding to the mating surface. The number of gates is ten. The dimple pattern of this golf ball is arranged by a hemisphere repetition arrangement method, and the number of units per hemisphere is five. This golf ball has 70 A dimples having a diameter of 4.1 mm, 210 B dimples having a diameter of 3.80 mm, and 130 C dimples having a diameter of 3.35 mm, similarly to the golf ball of the example. Have.
This golf ball has one great circle passage. This great circle passage exists in a portion corresponding to the equator E. That is, the portion shown by the two-dot chain line in FIG. 7 is the great circle passage.

[Flying distance test] A driver (W) equipped with a metal head on a swing robot manufactured by Tsuru Temper
# 1) was attached, and conditions were set so that the head speed was about 49 m / s. Next, 40 golf balls of the examples and comparative examples were prepared, and the golf balls were hit to measure the carry (carry). In each of the examples and comparative examples, 20 golf balls were hit so that the equator E was the fastest part of the backspin, and the remaining 20 golf balls were hit so that the longitude line was the fastest part of the backspin. . The average launch angle of the golf ball during this evaluation is about 11 °,
The rotation speed of the back spin was about 3000 rpm.
The wind direction during evaluation was almost tailwind, and the average wind speed was about 1 m / s. The average value of the flight distance is shown in Table 1 below.

[0039]

[Table 1]

From Table 1, it can be seen that the golf ball of the example has a smaller flight distance difference depending on the hitting position than the golf ball of the comparative example. It can also be seen that the golf ball of the example has a longer flight distance than the golf ball of the comparative example.
From the evaluation results, the superiority of the present invention is clear.

[0041]

As described above, the mold of the present invention can be easily manufactured. The golf ball obtained from this mold has excellent aerodynamic characteristics.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a golf ball mold according to one embodiment of the present invention.

FIG. 2 is a perspective view showing a lower mold of the mold shown in FIG. 1;

FIG. 3 is an enlarged view showing a part of the lower mold of FIG. 2;

FIG. 4 is a plan view showing a golf ball according to one embodiment of the present invention.

FIG. 5 is a front view showing the golf ball of FIG. 4;

FIG. 6 is a plan view showing a golf ball of a comparative example of the present invention.

FIG. 7 is a plan view showing the golf ball of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Upper mold 3 ... Lower mold 5 ... Cavity surface 7 ... Projection 9 ... Convex part 11 ... Concave part 13 ... Convex surface 15 ... Concave surface 17 ... Boundary surface 19: Gate A: A dimple B: B dimple C: C dimple E: Equator Pn: North pole Ps: South pole

Claims (6)

[Claims] 1. An upper mold and a lower mold having a large number of dimple-forming projections on a cavity surface thereof, and each of the upper mold and the lower mold is alternately arranged so that a mating surface with a counterpart becomes uneven. The number of the convex part of the upper die, the concave part of the upper die, the convex part of the lower die, and the concave part of the lower die are all three or more and five or less. There are two or more and eight or less protrusions in the first row from the mating surface in the portion. In each of the protrusions, at least one of the protrusions in the first row from the mating surface has the following formula ( A golf ball mold configured to satisfy I). R × 0.8 ≦ L ≦ R × 1.2 (I) (In the formula (I), R represents the radius of the projection, and L represents the vertical linear distance between the center of the projection and the mating surface.) Represents.) 2. The golf ball mold according to claim 1, wherein the projections are arranged such that there is no great circle path which is a great circle that does not intersect with the dimple on the surface of the molded golf ball. 3. The golf ball mold according to claim 1, wherein a gate for injecting molding material is provided at a position where the mating surface and the equatorial plane intersect. 4. In each of the upper mold and the lower mold,
The mating surface with the counterpart is a convex surface in the convex portion and substantially parallel to the equatorial surface, a concave surface in the concave portion and a boundary surface located between the convex surface and the concave surface substantially parallel to the equatorial surface, and all convex surfaces are The golf ball mold according to any one of claims 1 to 3, wherein each of the concave surfaces has the same area, and all of the concave surfaces have the same area. 5. In each of the upper mold and the lower mold,
The height difference between the highest convex part and the lowest concave part is 2.0 mm
The golf ball mold according to any one of claims 1 to 4, which is as follows. 6. A golf ball molded from the molding die according to any one of claims 1 to 5.